RESUMO
Pure chitosan, glutaraldehyde crosslinked chitosan, and a blend of chitosan with poly(ethylene oxide) (PEO) membranes were prepared. The three membranes were characterized in terms of their swelling capacities as well as their permeabilities to a drug model (sulfamerazine sodium salt). For the permeation experiments, the variables analyzed were the type of membrane and the initial drug concentration in the liquid phase (from 0.1% to 1.5%). Permeability coefficients were calculated using UV spectroscopy. The results showed that for the three analyzed membranes, the permeability did not change with time (over the studied time interval). An increase in the permeability for CHI/PEO membranes compared to those made of pure chitosan was also observed, possibly due to microporous region formation and/or crystallinity reduction. For the crosslinked membrane, an even higher increase in the permeability coefficient was observed. In this case, the increase was attributed to free volume variation.
Assuntos
Quitosana/química , Membranas Artificiais , Adsorção , Reagentes de Ligações Cruzadas , Cinética , Permeabilidade , Polietilenoglicóis , ÁguaRESUMO
Particulate systems composed of polyelectrolyte complexes (PEC) based on chitosan and poly(methacrylic acid) were obtained via template polymerization. The resultant particles were characterized as having regions with different charge densities: chitosan predominating in the core and poly(methacrylic acid) at the surface, the particles being negatively charged, as a consequence. Albumin was adsorbed on these particles (after cross-linking with glutardialdehyde), and pH was controlled to obtain two conditions: (i) adsorption of positively charged albumin and (ii) adsorption of albumin at its isoelectric point. Adsorption isotherms and zeta-potential measurements showed that albumin adsorption was controlled by hydrogen bonding/van der Waals interactions and that brush-like structures may enhance the adsorption of albumin on these particles. It was also found that shearing can induce desorption of albumin from the PEC surface, depending on the continuous phase albumin concentration.
Assuntos
Quitosana/química , Polímeros/química , Ácidos Polimetacrílicos/química , Soroalbumina Bovina/química , Adsorção , Eletrólitos/química , Glutaral/química , Ligação de Hidrogênio , Concentração de Íons de Hidrogênio , Espectroscopia de Infravermelho com Transformada de Fourier , Propriedades de Superfície , Difração de Raios XRESUMO
Chitosan/poly(methacrylic acid) complexes, CS/PMAA, were prepared via dropwise addition of a solution of PMAA to a solution of chitosan in acetic acid 2 wt %. The increase in molecular weight of PMAA inhibited the formation of insoluble complexes, while the increase in ionic strength first favored the formation of the complex followed by inhibiting it at higher concentrations. These observations were related to a description of polyelectrolyte complexation that was strongly dependent on macromolecular dimensions, both in terms of molecular weight and of coil expansion/contraction driven by polyelectrolyte effect.